During the past few days, I struggled with the silently manual install of DPM 2012 agent. Whatever the command I used, a popup screen appeared and I needed to validate Microsoft Sofware Licenses Terms... Very annoying :)
I tried various combinations like: /quiet, /q, /quiet /AcceptEula:yes...
An user from DPM forum pointed me to the right direction: /IAcceptEula
So log on to the protected computers, navigate to the network share, and then run the appropriate DPMAgentInstaller.exe command:
DpmAgentInstaller.exe [/q] [DPM server name] [/IAcceptEula]
This parameter is referenced in Technet link : Post-upgrade steps